Figure 4.6. QFN-40 Landing Diagram
Table 4.6. QFN-40 Landing Diagram Dimensions
All dimensions shown are in millimeters (mm) unless otherwise noted.
Dimension and Tolerancing is per the ANSI Y14.5M-1994 specification.
This Land Pattern Design is based on the IPC-SM-7351 guidelines.
All dimensions shown are at Maximum Material Condition (MMC). Least Material Condition (LMC) is
calculated based on a Fabrication Allowance of 0.05 mm.
Solder Mask Design
All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the
metal pad is to be 60
m minimum, all the way around the pad.
A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure
good solder paste release.
The stencil thickness should be 0.125 mm (5 mils).
The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pads.
A 4x4 array of 0.80 mm square openings on a 1.05 mm pitch should be used for the center ground pad.
A No-Clean, Type-3 solder paste is recommended.
Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body